Noise Reduction Manual

Noise level low medium high the low and medium noise

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Unformatted text preview: This often results in fewer artifacts. However, Low and Medium settings will increase usage of the computer’s processor that may result in not being able to preview in real-time. When set to High, the algorithm will not try to “split” the audio into noisy and non-noisy parts before removing clicks. In addition, the High setting uses less of the computer’s processor, so we recommend the High setting for slower computers. However, some source material (especially low voice and horns) can sometimes cause the detection algorithm to misinterpret data and results in audible artifacts. At Low and Medium settings, the audio input is split into noise and non-noise portions, and clicks are removed from only the noisy part of the audio. This often results in fewer artifacts. However, CPU usage will increase, and some users will not be able to preview in real time. CLICK AND CRACKLE REMOVAL CHP. 3 39 Remove low-frequency rumble When enabled, the very low frequencies (below 30 Hz) will be removed. This often helps the detection algorithm work more efficiently. When enabled, the output waveform can look different from the original. This difference is due to the large amounts of low frequency noise present in older recordings (generated from slightly warped discs). Removing this noise is usually completely inaudible and prevents your speakers from reproducing sounds you can not hear. When removing clicks from a small selection (one second of audio), make sure to disable this function to more easily preserve waveform continuity at the endpoints. Keep residual output When enabled, only the sound being removed is audible. This is useful for determining how accurately the detection algorithm is performing or whether the algorithm is removing any of the sound that you want to keep. CHP. 3 CLICK AND CRACKLE REMOVAL 40 CLICK AND CRACKLE REMOVAL CHP. 3 41 CHAPTER Vinyl Restoration 4 Sonic Foundry Vinyl Restoration is designed to remove both impulsive (pops and clicks) and broadband surface noise from old recordings simultaneously. An advanced filtering technique detects and automatically removes the very fast transients generated by dirt and scratches in the surface of a record. Then, a method similar to the Noise Reduction function is used to minimize the audibility of broadband surface noise inherent in older recordings. Limitations The first thing you should realize is that a restored recording will never be perfect; you should concentrate on making it as enjoyable to listen to as possible. Most listeners do not mind a little hiss or a muffled pop. However, anything that sounds very unnatural can become very distracting. Moderation is the key. Using Vinyl Restoration The Vinyl Restoration dialog is easy to use for eliminating surface noise. CHP. 4 VINYL RESTORATION 42 Removing surface noise Removing surface noise is an experimental process; the settings will almost always need to be adjusted for the specific material you are processing. The Reduce noise by, Affect frequencies above, and Noise floor sliders are the three main controls used in achieving the noise reduction you prefer. However, you will need to compromise between how much noise is reduced and how much high-frequency is lost. To remove surface noise, do the following: 1. With the Reduce noise by value set to -8 dB and Affect frequencies above set to 2000 Hz, start raising the Noise floor slider until the high-frequency noise is noticeably reduced. 2. Increase or decrease the amount of noise reduction with the Reduce noise by slider. No reduction will occur if you set the control to 0 dB. Setting this value much higher than 15 dB can cause undesirable artifacts and too much high-frequency loss. 3. Use the Affect frequencies above slider to determine the frequency level that the Reduce noise by value affects. For example, you may apply noise reduction to high frequencies by setting the Affect frequencies above value to 8,000 Hz. This setting is useful when source material is being adversely affected by the amount of reduction you are trying to achieve. Note: If a lot of broadband noise remains after running the Vinyl Restoration, try using Vinyl Restoration without any noise reduction (0 dB). Then, use Noise Reduction to improve the signal-to-noise ratio. VINYL RESTORATION CHP. 4 43 Removing clicks Removing clicks is as easy as moving the Click removal amount slider. This control determines the sensitivity of the click and crackle removal algorithm. The default setting of 10 usually works well for most applications. A larger number will remove more clicks, but may also reduce some transient material that you would like to keep (such as drum hits). If you begin to notice wanted transients being reduced, decrease the Click removal amount. For extra glitch-free recording, use the Sonic Foundry Click and Crackle Removal plug-in before and after running the Vinyl Restoration function. For more information, see Click and Crackle Removal on page 35. For some applications, it may be useful to manually remove some of the largest pops before processing. Vinyl Restoration reference This section de...
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This note was uploaded on 05/15/2013 for the course EMUS 201 taught by Professor Pardal during the Winter '10 term at Life.

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